233. Moreover, certain plants regularly produce _neutral flowers_, consisting of floral envelopes only. In Fig. 214, some are seen around the margin of the cyme in Hydrangea. They are likewise familiar in the Hobble-bush and in Wild-Cranberry tree, Viburnum Oxycoccus; where they form an attractive setting to the cluster of small and comparatively inconspicuous perfect flowers which they adorn. In the Guelder Rose, or Snow-ball of ornamental cultivation, all or most of the blossoms of this same shrub are transformed into neutral flowers. [Illustration: Fig. 218. A _flos plenus_, namely, a full double flower of Rose.] 234. =The Essential Organs= are likewise of two kinds, placed one above or within the other; namely, first, the STAMENS or fertilizing organs, and second, the PISTILS, which are to be fertilized and bear the seeds. [Illustration: Fig. 219. A stamen: _a_, filament; _b_, anther, discharging pollen.] [Illustration: Fig. 220. A pistil; with ovary, _a_, half cut away, to show the contained ovules; _b_, style; _c_, stigma.] 235. =A Stamen= consists of two parts, namely, the FILAMENT or stalk (Fig. 219 _a_), and the ANTHER (_b_). The latter is the only essential part. It is a case, commonly with two lobes or cells, each opening lengthwise by a slit, at the proper time, and discharging a powder or dust-like substance, usually of a yellow color. This powder is the POLLEN, or fertilizing matter, to produce which is the office of the stamen. 236. =A Pistil= (Fig. 220, 221) when complete, has three parts; OVARY, STYLE, and STIGMA. The _Ovary_, at base, is the hollow portion, which contains one or more OVULES or rudimentary seeds. The _Style_ is the tapering portion above: the _Stigma_ is a portion of the style, usually its tip, with moist naked surface, upon which grains of pollen may lodge and adhere, and thence make a growth which extends down to the ovules. When there is no style then the stigma occupies the tip of the ovary. [Illustration: Fig. 221. Model of a simple pistil, with ovary cut across and slightly opened ventrally, to show the ovules and their attachment.] 237. =The Torus= or =Receptacle= is the end of the flower-stalk, or the portion of axis or stem out of which the several organs of the flower grow, upon which they are borne (Fig. 223). [Illustration: Fig. 222. Flower of Sedum ternatum, a Stonecrop.] [Illustration: Fig. 223. Parts of same, two of each kind, separated and displayed; the torus or receptacle in the centre; _a_, a sepal; _b_, a petal; _c_, a stamen; _d_, a pistil.]